mm/page_owner.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 #include <linux/debugfs.h>
   3 #include <linux/mm.h>
   4 #include <linux/slab.h>
   5 #include <linux/uaccess.h>
   6 #include <linux/memblock.h>
   7 #include <linux/stacktrace.h>
   8 #include <linux/page_owner.h>
   9 #include <linux/jump_label.h>
  10 #include <linux/migrate.h>
  11 #include <linux/stackdepot.h>
  12 #include <linux/seq_file.h>
  13 #include <linux/sched/clock.h>
  14
  15 #include "internal.h"
  16
  17 /*
  18  * TODO: teach PAGE_OWNER_STACK_DEPTH (__dump_page_owner and save_stack)
  19  * to use off stack temporal storage
  20  */
  21 #define PAGE_OWNER_STACK_DEPTH (16)
  22
  23 struct page_owner {
  24         unsigned short order;
  25         short last_migrate_reason;
  26         gfp_t gfp_mask;
  27         depot_stack_handle_t handle;
  28         depot_stack_handle_t free_handle;
  29         u64 ts_nsec;
  30         u64 free_ts_nsec;
  31         pid_t pid;
  32 };
  33
  34 static bool page_owner_enabled = false;
  35 DEFINE_STATIC_KEY_FALSE(page_owner_inited);
  36
  37 static depot_stack_handle_t dummy_handle;
  38 static depot_stack_handle_t failure_handle;
  39 static depot_stack_handle_t early_handle;
  40
  41 static void init_early_allocated_pages(void);
  42
  43 static int __init early_page_owner_param(char *buf)
  44 {
  45         return kstrtobool(buf, &page_owner_enabled);
  46 }
  47 early_param("page_owner", early_page_owner_param);
  48
  49 static bool need_page_owner(void)
  50 {
  51         return page_owner_enabled;
  52 }
  53
  54 static __always_inline depot_stack_handle_t create_dummy_stack(void)
  55 {
  56         unsigned long entries[4];
  57         unsigned int nr_entries;
  58
  59         nr_entries = stack_trace_save(entries, ARRAY_SIZE(entries), 0);
  60         return stack_depot_save(entries, nr_entries, GFP_KERNEL);
  61 }
  62
  63 static noinline void register_dummy_stack(void)
  64 {
  65         dummy_handle = create_dummy_stack();
  66 }
  67
  68 static noinline void register_failure_stack(void)
  69 {
  70         failure_handle = create_dummy_stack();
  71 }
  72
  73 static noinline void register_early_stack(void)
  74 {
  75         early_handle = create_dummy_stack();
  76 }
  77
  78 static void init_page_owner(void)
  79 {
  80         if (!page_owner_enabled)
  81                 return;
  82
  83         register_dummy_stack();
  84         register_failure_stack();
  85         register_early_stack();
  86         static_branch_enable(&page_owner_inited);
  87         init_early_allocated_pages();
  88 }
  89
  90 struct page_ext_operations page_owner_ops = {
  91         .size = sizeof(struct page_owner),
  92         .need = need_page_owner,
  93         .init = init_page_owner,
  94 };
  95
  96 static inline struct page_owner *get_page_owner(struct page_ext *page_ext)
  97 {
  98         return (void *)page_ext + page_owner_ops.offset;
  99 }
 100
 101 static noinline depot_stack_handle_t save_stack(gfp_t flags)
 102 {
 103         unsigned long entries[PAGE_OWNER_STACK_DEPTH];
 104         depot_stack_handle_t handle;
 105         unsigned int nr_entries;
 106
 107         /*
 108          * Avoid recursion.
 109          *
 110          * Sometimes page metadata allocation tracking requires more
 111          * memory to be allocated:
 112          * - when new stack trace is saved to stack depot
 113          * - when backtrace itself is calculated (ia64)
 114          */
 115         if (current->in_page_owner)
 116                 return dummy_handle;
 117         current->in_page_owner = 1;
 118
 119         nr_entries = stack_trace_save(entries, ARRAY_SIZE(entries), 2);
 120         handle = stack_depot_save(entries, nr_entries, flags);
 121         if (!handle)
 122                 handle = failure_handle;
 123
 124         current->in_page_owner = 0;
 125         return handle;
 126 }
 127
 128 void __reset_page_owner(struct page *page, unsigned int order)
 129 {
 130         int i;
 131         struct page_ext *page_ext;
 132         depot_stack_handle_t handle;
 133         struct page_owner *page_owner;
 134         u64 free_ts_nsec = local_clock();
 135
 136         page_ext = lookup_page_ext(page);
 137         if (unlikely(!page_ext))
 138                 return;
 139
 140         handle = save_stack(GFP_NOWAIT | __GFP_NOWARN);
 141         for (i = 0; i < (1 << order); i++) {
 142                 __clear_bit(PAGE_EXT_OWNER_ALLOCATED, &page_ext->flags);
 143                 page_owner = get_page_owner(page_ext);
 144                 page_owner->free_handle = handle;
 145                 page_owner->free_ts_nsec = free_ts_nsec;
 146                 page_ext = page_ext_next(page_ext);
 147         }
 148 }
 149
 150 static inline void __set_page_owner_handle(struct page_ext *page_ext,
 151                                         depot_stack_handle_t handle,
 152                                         unsigned int order, gfp_t gfp_mask)
 153 {
 154         struct page_owner *page_owner;
 155         int i;
 156
 157         for (i = 0; i < (1 << order); i++) {
 158                 page_owner = get_page_owner(page_ext);
 159                 page_owner->handle = handle;
 160                 page_owner->order = order;
 161                 page_owner->gfp_mask = gfp_mask;
 162                 page_owner->last_migrate_reason = -1;
 163                 page_owner->pid = current->pid;
 164                 page_owner->ts_nsec = local_clock();
 165                 __set_bit(PAGE_EXT_OWNER, &page_ext->flags);
 166                 __set_bit(PAGE_EXT_OWNER_ALLOCATED, &page_ext->flags);
 167
 168                 page_ext = page_ext_next(page_ext);
 169         }
 170 }
 171
 172 noinline void __set_page_owner(struct page *page, unsigned int order,
 173                                         gfp_t gfp_mask)
 174 {
 175         struct page_ext *page_ext = lookup_page_ext(page);
 176         depot_stack_handle_t handle;
 177
 178         if (unlikely(!page_ext))
 179                 return;
 180
 181         handle = save_stack(gfp_mask);
 182         __set_page_owner_handle(page_ext, handle, order, gfp_mask);
 183 }
 184
 185 void __set_page_owner_migrate_reason(struct page *page, int reason)
 186 {
 187         struct page_ext *page_ext = lookup_page_ext(page);
 188         struct page_owner *page_owner;
 189
 190         if (unlikely(!page_ext))
 191                 return;
 192
 193         page_owner = get_page_owner(page_ext);
 194         page_owner->last_migrate_reason = reason;
 195 }
 196
 197 void __split_page_owner(struct page *page, unsigned int nr)
 198 {
 199         int i;
 200         struct page_ext *page_ext = lookup_page_ext(page);
 201         struct page_owner *page_owner;
 202
 203         if (unlikely(!page_ext))
 204                 return;
 205
 206         for (i = 0; i < nr; i++) {
 207                 page_owner = get_page_owner(page_ext);
 208                 page_owner->order = 0;
 209                 page_ext = page_ext_next(page_ext);
 210         }
 211 }
 212
 213 void __copy_page_owner(struct page *oldpage, struct page *newpage)
 214 {
 215         struct page_ext *old_ext = lookup_page_ext(oldpage);
 216         struct page_ext *new_ext = lookup_page_ext(newpage);
 217         struct page_owner *old_page_owner, *new_page_owner;
 218
 219         if (unlikely(!old_ext || !new_ext))
 220                 return;
 221
 222         old_page_owner = get_page_owner(old_ext);
 223         new_page_owner = get_page_owner(new_ext);
 224         new_page_owner->order = old_page_owner->order;
 225         new_page_owner->gfp_mask = old_page_owner->gfp_mask;
 226         new_page_owner->last_migrate_reason =
 227                 old_page_owner->last_migrate_reason;
 228         new_page_owner->handle = old_page_owner->handle;
 229         new_page_owner->pid = old_page_owner->pid;
 230         new_page_owner->ts_nsec = old_page_owner->ts_nsec;
 231         new_page_owner->free_ts_nsec = old_page_owner->ts_nsec;
 232
 233         /*
 234          * We don't clear the bit on the oldpage as it's going to be freed
 235          * after migration. Until then, the info can be useful in case of
 236          * a bug, and the overall stats will be off a bit only temporarily.
 237          * Also, migrate_misplaced_transhuge_page() can still fail the
 238          * migration and then we want the oldpage to retain the info. But
 239          * in that case we also don't need to explicitly clear the info from
 240          * the new page, which will be freed.
 241          */
 242         __set_bit(PAGE_EXT_OWNER, &new_ext->flags);
 243         __set_bit(PAGE_EXT_OWNER_ALLOCATED, &new_ext->flags);
 244 }
 245
 246 void pagetypeinfo_showmixedcount_print(struct seq_file *m,
 247                                        pg_data_t *pgdat, struct zone *zone)
 248 {
 249         struct page *page;
 250         struct page_ext *page_ext;
 251         struct page_owner *page_owner;
 252         unsigned long pfn, block_end_pfn;
 253         unsigned long end_pfn = zone_end_pfn(zone);
 254         unsigned long count[MIGRATE_TYPES] = { 0, };
 255         int pageblock_mt, page_mt;
 256         int i;
 257
 258         /* Scan block by block. First and last block may be incomplete */
 259         pfn = zone->zone_start_pfn;
 260
 261         /*
 262          * Walk the zone in pageblock_nr_pages steps. If a page block spans
 263          * a zone boundary, it will be double counted between zones. This does
 264          * not matter as the mixed block count will still be correct
 265          */
 266         for (; pfn < end_pfn; ) {
 267                 page = pfn_to_online_page(pfn);
 268                 if (!page) {
 269                         pfn = ALIGN(pfn + 1, MAX_ORDER_NR_PAGES);
 270                         continue;
 271                 }
 272
 273                 block_end_pfn = ALIGN(pfn + 1, pageblock_nr_pages);
 274                 block_end_pfn = min(block_end_pfn, end_pfn);
 275
 276                 pageblock_mt = get_pageblock_migratetype(page);
 277
 278                 for (; pfn < block_end_pfn; pfn++) {
 279                         if (!pfn_valid_within(pfn))
 280                                 continue;
 281
 282                         /* The pageblock is online, no need to recheck. */
 283                         page = pfn_to_page(pfn);
 284
 285                         if (page_zone(page) != zone)
 286                                 continue;
 287
 288                         if (PageBuddy(page)) {
 289                                 unsigned long freepage_order;
 290
 291                                 freepage_order = buddy_order_unsafe(page);
 292                                 if (freepage_order < MAX_ORDER)
 293                                         pfn += (1UL << freepage_order) - 1;
 294                                 continue;
 295                         }
 296
 297                         if (PageReserved(page))
 298                                 continue;
 299
 300                         page_ext = lookup_page_ext(page);
 301                         if (unlikely(!page_ext))
 302                                 continue;
 303
 304                         if (!test_bit(PAGE_EXT_OWNER_ALLOCATED, &page_ext->flags))
 305                                 continue;
 306
 307                         page_owner = get_page_owner(page_ext);
 308                         page_mt = gfp_migratetype(page_owner->gfp_mask);
 309                         if (pageblock_mt != page_mt) {
 310                                 if (is_migrate_cma(pageblock_mt))
 311                                         count[MIGRATE_MOVABLE]++;
 312                                 else
 313                                         count[pageblock_mt]++;
 314
 315                                 pfn = block_end_pfn;
 316                                 break;
 317                         }
 318                         pfn += (1UL << page_owner->order) - 1;
 319                 }
 320         }
 321
 322         /* Print counts */
 323         seq_printf(m, "Node %d, zone %8s ", pgdat->node_id, zone->name);
 324         for (i = 0; i < MIGRATE_TYPES; i++)
 325                 seq_printf(m, "%12lu ", count[i]);
 326         seq_putc(m, '\n');
 327 }
 328
 329 static ssize_t
 330 print_page_owner(char __user *buf, size_t count, unsigned long pfn,
 331                 struct page *page, struct page_owner *page_owner,
 332                 depot_stack_handle_t handle)
 333 {
 334         int ret, pageblock_mt, page_mt;
 335         unsigned long *entries;
 336         unsigned int nr_entries;
 337         char *kbuf;
 338
 339         count = min_t(size_t, count, PAGE_SIZE);
 340         kbuf = kmalloc(count, GFP_KERNEL);
 341         if (!kbuf)
 342                 return -ENOMEM;
 343
 344         ret = snprintf(kbuf, count,
 345                         "Page allocated via order %u, mask %#x(%pGg), pid %d, ts %llu ns, free_ts %llu ns\n",
 346                         page_owner->order, page_owner->gfp_mask,
 347                         &page_owner->gfp_mask, page_owner->pid,
 348                         page_owner->ts_nsec, page_owner->free_ts_nsec);
 349
 350         if (ret >= count)
 351                 goto err;
 352
 353         /* Print information relevant to grouping pages by mobility */
 354         pageblock_mt = get_pageblock_migratetype(page);
 355         page_mt  = gfp_migratetype(page_owner->gfp_mask);
 356         ret += snprintf(kbuf + ret, count - ret,
 357                         "PFN %lu type %s Block %lu type %s Flags %#lx(%pGp)\n",
 358                         pfn,
 359                         migratetype_names[page_mt],
 360                         pfn >> pageblock_order,
 361                         migratetype_names[pageblock_mt],
 362                         page->flags, &page->flags);
 363
 364         if (ret >= count)
 365                 goto err;
 366
 367         nr_entries = stack_depot_fetch(handle, &entries);
 368         ret += stack_trace_snprint(kbuf + ret, count - ret, entries, nr_entries, 0);
 369         if (ret >= count)
 370                 goto err;
 371
 372         if (page_owner->last_migrate_reason != -1) {
 373                 ret += snprintf(kbuf + ret, count - ret,
 374                         "Page has been migrated, last migrate reason: %s\n",
 375                         migrate_reason_names[page_owner->last_migrate_reason]);
 376                 if (ret >= count)
 377                         goto err;
 378         }
 379
 380         ret += snprintf(kbuf + ret, count - ret, "\n");
 381         if (ret >= count)
 382                 goto err;
 383
 384         if (copy_to_user(buf, kbuf, ret))
 385                 ret = -EFAULT;
 386
 387         kfree(kbuf);
 388         return ret;
 389
 390 err:
 391         kfree(kbuf);
 392         return -ENOMEM;
 393 }
 394
 395 void __dump_page_owner(const struct page *page)
 396 {
 397         struct page_ext *page_ext = lookup_page_ext(page);
 398         struct page_owner *page_owner;
 399         depot_stack_handle_t handle;
 400         unsigned long *entries;
 401         unsigned int nr_entries;
 402         gfp_t gfp_mask;
 403         int mt;
 404
 405         if (unlikely(!page_ext)) {
 406                 pr_alert("There is not page extension available.\n");
 407                 return;
 408         }
 409
 410         page_owner = get_page_owner(page_ext);
 411         gfp_mask = page_owner->gfp_mask;
 412         mt = gfp_migratetype(gfp_mask);
 413
 414         if (!test_bit(PAGE_EXT_OWNER, &page_ext->flags)) {
 415                 pr_alert("page_owner info is not present (never set?)\n");
 416                 return;
 417         }
 418
 419         if (test_bit(PAGE_EXT_OWNER_ALLOCATED, &page_ext->flags))
 420                 pr_alert("page_owner tracks the page as allocated\n");
 421         else
 422                 pr_alert("page_owner tracks the page as freed\n");
 423
 424         pr_alert("page last allocated via order %u, migratetype %s, gfp_mask %#x(%pGg), pid %d, ts %llu, free_ts %llu\n",
 425                  page_owner->order, migratetype_names[mt], gfp_mask, &gfp_mask,
 426                  page_owner->pid, page_owner->ts_nsec, page_owner->free_ts_nsec);
 427
 428         handle = READ_ONCE(page_owner->handle);
 429         if (!handle) {
 430                 pr_alert("page_owner allocation stack trace missing\n");
 431         } else {
 432                 nr_entries = stack_depot_fetch(handle, &entries);
 433                 stack_trace_print(entries, nr_entries, 0);
 434         }
 435
 436         handle = READ_ONCE(page_owner->free_handle);
 437         if (!handle) {
 438                 pr_alert("page_owner free stack trace missing\n");
 439         } else {
 440                 nr_entries = stack_depot_fetch(handle, &entries);
 441                 pr_alert("page last free stack trace:\n");
 442                 stack_trace_print(entries, nr_entries, 0);
 443         }
 444
 445         if (page_owner->last_migrate_reason != -1)
 446                 pr_alert("page has been migrated, last migrate reason: %s\n",
 447                         migrate_reason_names[page_owner->last_migrate_reason]);
 448 }
 449
 450 static ssize_t
 451 read_page_owner(struct file *file, char __user *buf, size_t count, loff_t *ppos)
 452 {
 453         unsigned long pfn;
 454         struct page *page;
 455         struct page_ext *page_ext;
 456         struct page_owner *page_owner;
 457         depot_stack_handle_t handle;
 458
 459         if (!static_branch_unlikely(&page_owner_inited))
 460                 return -EINVAL;
 461
 462         page = NULL;
 463         pfn = min_low_pfn + *ppos;
 464
 465         /* Find a valid PFN or the start of a MAX_ORDER_NR_PAGES area */
 466         while (!pfn_valid(pfn) && (pfn & (MAX_ORDER_NR_PAGES - 1)) != 0)
 467                 pfn++;
 468
 469         drain_all_pages(NULL);
 470
 471         /* Find an allocated page */
 472         for (; pfn < max_pfn; pfn++) {
 473                 /*
 474                  * If the new page is in a new MAX_ORDER_NR_PAGES area,
 475                  * validate the area as existing, skip it if not
 476                  */
 477                 if ((pfn & (MAX_ORDER_NR_PAGES - 1)) == 0 && !pfn_valid(pfn)) {
 478                         pfn += MAX_ORDER_NR_PAGES - 1;
 479                         continue;
 480                 }
 481
 482                 /* Check for holes within a MAX_ORDER area */
 483                 if (!pfn_valid_within(pfn))
 484                         continue;
 485
 486                 page = pfn_to_page(pfn);
 487                 if (PageBuddy(page)) {
 488                         unsigned long freepage_order = buddy_order_unsafe(page);
 489
 490                         if (freepage_order < MAX_ORDER)
 491                                 pfn += (1UL << freepage_order) - 1;
 492                         continue;
 493                 }
 494
 495                 page_ext = lookup_page_ext(page);
 496                 if (unlikely(!page_ext))
 497                         continue;
 498
 499                 /*
 500                  * Some pages could be missed by concurrent allocation or free,
 501                  * because we don't hold the zone lock.
 502                  */
 503                 if (!test_bit(PAGE_EXT_OWNER, &page_ext->flags))
 504                         continue;
 505
 506                 /*
 507                  * Although we do have the info about past allocation of free
 508                  * pages, it's not relevant for current memory usage.
 509                  */
 510                 if (!test_bit(PAGE_EXT_OWNER_ALLOCATED, &page_ext->flags))
 511                         continue;
 512
 513                 page_owner = get_page_owner(page_ext);
 514
 515                 /*
 516                  * Don't print "tail" pages of high-order allocations as that
 517                  * would inflate the stats.
 518                  */
 519                 if (!IS_ALIGNED(pfn, 1 << page_owner->order))
 520                         continue;
 521
 522                 /*
 523                  * Access to page_ext->handle isn't synchronous so we should
 524                  * be careful to access it.
 525                  */
 526                 handle = READ_ONCE(page_owner->handle);
 527                 if (!handle)
 528                         continue;
 529
 530                 /* Record the next PFN to read in the file offset */
 531                 *ppos = (pfn - min_low_pfn) + 1;
 532
 533                 return print_page_owner(buf, count, pfn, page,
 534                                 page_owner, handle);
 535         }
 536
 537         return 0;
 538 }
 539
 540 static void init_pages_in_zone(pg_data_t *pgdat, struct zone *zone)
 541 {
 542         unsigned long pfn = zone->zone_start_pfn;
 543         unsigned long end_pfn = zone_end_pfn(zone);
 544         unsigned long count = 0;
 545
 546         /*
 547          * Walk the zone in pageblock_nr_pages steps. If a page block spans
 548          * a zone boundary, it will be double counted between zones. This does
 549          * not matter as the mixed block count will still be correct
 550          */
 551         for (; pfn < end_pfn; ) {
 552                 unsigned long block_end_pfn;
 553
 554                 if (!pfn_valid(pfn)) {
 555                         pfn = ALIGN(pfn + 1, MAX_ORDER_NR_PAGES);
 556                         continue;
 557                 }
 558
 559                 block_end_pfn = ALIGN(pfn + 1, pageblock_nr_pages);
 560                 block_end_pfn = min(block_end_pfn, end_pfn);
 561
 562                 for (; pfn < block_end_pfn; pfn++) {
 563                         struct page *page;
 564                         struct page_ext *page_ext;
 565
 566                         if (!pfn_valid_within(pfn))
 567                                 continue;
 568
 569                         page = pfn_to_page(pfn);
 570
 571                         if (page_zone(page) != zone)
 572                                 continue;
 573
 574                         /*
 575                          * To avoid having to grab zone->lock, be a little
 576                          * careful when reading buddy page order. The only
 577                          * danger is that we skip too much and potentially miss
 578                          * some early allocated pages, which is better than
 579                          * heavy lock contention.
 580                          */
 581                         if (PageBuddy(page)) {
 582                                 unsigned long order = buddy_order_unsafe(page);
 583
 584                                 if (order > 0 && order < MAX_ORDER)
 585                                         pfn += (1UL << order) - 1;
 586                                 continue;
 587                         }
 588
 589                         if (PageReserved(page))
 590                                 continue;
 591
 592                         page_ext = lookup_page_ext(page);
 593                         if (unlikely(!page_ext))
 594                                 continue;
 595
 596                         /* Maybe overlapping zone */
 597                         if (test_bit(PAGE_EXT_OWNER, &page_ext->flags))
 598                                 continue;
 599
 600                         /* Found early allocated page */
 601                         __set_page_owner_handle(page_ext, early_handle,
 602                                                 0, 0);
 603                         count++;
 604                 }
 605                 cond_resched();
 606         }
 607
 608         pr_info("Node %d, zone %8s: page owner found early allocated %lu pages\n",
 609                 pgdat->node_id, zone->name, count);
 610 }
 611
 612 static void init_zones_in_node(pg_data_t *pgdat)
 613 {
 614         struct zone *zone;
 615         struct zone *node_zones = pgdat->node_zones;
 616
 617         for (zone = node_zones; zone - node_zones < MAX_NR_ZONES; ++zone) {
 618                 if (!populated_zone(zone))
 619                         continue;
 620
 621                 init_pages_in_zone(pgdat, zone);
 622         }
 623 }
 624
 625 static void init_early_allocated_pages(void)
 626 {
 627         pg_data_t *pgdat;
 628
 629         for_each_online_pgdat(pgdat)
 630                 init_zones_in_node(pgdat);
 631 }
 632
 633 static const struct file_operations proc_page_owner_operations = {
 634         .read           = read_page_owner,
 635 };
 636
 637 static int __init pageowner_init(void)
 638 {
 639         if (!static_branch_unlikely(&page_owner_inited)) {
 640                 pr_info("page_owner is disabled\n");
 641                 return 0;
 642         }
 643
 644         debugfs_create_file("page_owner", 0400, NULL, NULL,
 645                             &proc_page_owner_operations);
 646
 647         return 0;
 648 }
 649 late_initcall(pageowner_init)